When articles are manufactured from strip material in a stamping and forming machine, it is frequently necessary to trim one or both edges of the strip material. Edge trimming of the strip may be required for the reason that the physical properties of edge portions of the strip (such as elastic modulus and hardness) may be different from the corresponding properties required in the finished articles and which are to be found in central portions of the strip which are spaced from the edge. Also, under some circumstances it is necessary to reduce the width of the strip by an amount required by the dimensions in the finished strip containing the articles. The trimming of the edges is carried out by means of punches and dies which punch slugs from the edges while the strip is intermittently fed past the punches and dies in the stamping and forming machine.
The small pieces of scrap metal, commonly called slugs, which are produced in a stamping and forming machine must be removed from the vicinity of the punches and dies. If the material is relatively thick so that the slugs are heavy, and if the stamping and forming machine is of the conventional type, in which a punch assembly reciprocates vertically towards and away from a fixed die assembly, the relatively heavy slugs will fall through openings in the die assembly and thereby be eliminated by gravity. However, if the material is extremely thin, say 0.008 inches (0.2O mm) or less, the slugs will tend to adhere to each other and to the walls of the passageway into which they are pushed by the punch and become packed in the passageway. The result can be that the passageway will become jammed with compacted slugs and breakage of the punches can occur when the slugs entirely fill the passageway. This problem can be overcome in a conventional stamping and forming machine of the type having a vertically reciprocal punch assembly and a fixed die by the use of a suction system in the passageway through which the slugs pass.
There are disadvantages to the use of suction systems as a means of slug elimination in stamping and forming machines. Such systems require that there be a continuous supply of compressed air and therefore require energy to run the air compressor. The compressed air is exhausted into the room in which the machine is located and are a source of air pollution for the reason that the air from the compressor carries lubricant from the compressor. In a machine of the type shown in U.S. Pat. No. 4,497,196, the fact that the die assembly, as well as the punch assembly, reciprocates makes the provision of the tubing for a suction system difficult.
When the slugs are produced by punching openings which are spaced from the side edges of the strip, the slugs can be eliminated in a machine of the type shown in U.S. Pat. No. 4,497,196 by methods described in U.S. Pat. No. 4,809,576. That patent shows the manner in which slugs can be pushed through a passageway in the die ram block to a cavity through which an endless belt passes. The belt is designed such that it carries the slugs from the end o the passageway in the die block laterally to an external location where they are disposed of. The system described in U.S. Pat. No. 4,809,576 requires, however, that the passageway extends through the die plate and the die ram block closely conform to the shape of the slugs so that the slugs will be maintained in an orderly stack as they are advanced through the passageway by the punch; in other words, during each operating cycle, the punch will punch a slug from the strip material, push it into the die opening, and thereby exert a force on the stack of slugs in the die opening and the passageway so that the stack will move progressively to the cavity and to the belt.
An additional problem is caused by the fact that slugs which are produced in a trimming operation will not always be of the same dimensions for the reason that the width of strip material will vary within some predetermined tolerance limits, usually about .+-.0.002 inches (.+-.0.051 mm). The die opening and the aligned passageway in the die ram block must be sufficiently large to accommodate the widest slug which may be produced from strip material having some given nominal width and if the passageway and the die opening are so dimensioned, the wide slugs may be eliminated as described above. However, if the strip material is at the lower limit of the tolerance range, the width of the slugs will be somewhat less than the width of the slugs produced from material at the upper limit and the die opening and the passageway will be oversized relative to the width of the slugs. Under these circumstances, the slugs will not necessarily be neatly stacked as required but may become jammed or packed in the die opening or in the passageway as discussed above.
The present invention is directed to the achievement of punch and die combinations with which edge portions of strip material can be trimmed regardless of the width of the strip (within predetermined tolerance limits) without packing or jamming of slugs in the slug receiving die opening and passageway in the die plate and the die ram block.